Port pred4x4_down_left_mmxext (H.264 intra prediction) from x264 to FFmpeg.

LGPL relicensing approved by original authors: Holger Lubitz <holger lubitz
org>, Jason Garrett-Glaser <darkshikari gmail com> and Loren Merritt <lorenm
at u dot washington dot edu>. Patch by Daniel Kang <daniel dot d dot kang at
gmail com>, as part of Google's GCI 2010.

Originally committed as revision 26087 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/x86/h264_intrapred.asm

@@ -1104,3 +1104,31 @@ cglobal pred4x4_vertical_vp8_mmxext, 3,3
     movd [r1+r2*1], m3
     movd [r1+r2*2], m3
     RET
+
+;-----------------------------------------------------------------------------
+; void pred4x4_down_left_mmxext(uint8_t *src, const uint8_t *topright, int stride)
+;-----------------------------------------------------------------------------
+
+INIT_MMX
+cglobal pred4x4_down_left_mmxext, 3,3
+    sub       r0, r2
+    movq      m1, [r0]
+    punpckldq m1, [r1]
+    movq      m2, m1
+    movq      m3, m1
+    movq      m4, m1
+    psllq     m1, 8
+    pxor      m2, m1
+    psrlq     m2, 8
+    pxor      m3, m2
+    PRED4x4_LOWPASS m0, m1, m3, m4, m5
+    lea       r1, [r0+r2*2]
+    psrlq     m0, 8
+    movd      [r0+r2*1], m0
+    psrlq     m0, 8
+    movd      [r0+r2*2], m0
+    psrlq     m0, 8
+    movd      [r1+r2*1], m0
+    psrlq     m0, 8
+    movd      [r1+r2*2], m0
+    RET

libavcodec/x86/h264_intrapred_init.c

@@ -58,6 +58,7 @@ void ff_pred8x8_tm_vp8_mmxext      (uint8_t *src, int stride);
 void ff_pred8x8_tm_vp8_sse2        (uint8_t *src, int stride);
 void ff_pred8x8_tm_vp8_ssse3       (uint8_t *src, int stride);
 void ff_pred4x4_dc_mmxext          (uint8_t *src, const uint8_t *topright, int stride);
+void ff_pred4x4_down_left_mmxext   (uint8_t *src, const uint8_t *topright, int stride);
 void ff_pred4x4_tm_vp8_mmx         (uint8_t *src, const uint8_t *topright, int stride);
 void ff_pred4x4_tm_vp8_mmxext      (uint8_t *src, const uint8_t *topright, int stride);
 void ff_pred4x4_tm_vp8_ssse3       (uint8_t *src, const uint8_t *topright, int stride);
@@ -94,6 +95,8 @@ void ff_h264_pred_init_x86(H264PredContext *h, int codec_id)
         h->pred16x16[DC_PRED8x8  ] = ff_pred16x16_dc_mmxext;
         h->pred8x8  [HOR_PRED8x8 ] = ff_pred8x8_horizontal_mmxext;
         h->pred4x4  [DC_PRED     ] = ff_pred4x4_dc_mmxext;
+        if (codec_id == CODEC_ID_VP8 || codec_id == CODEC_ID_H264)
+            h->pred4x4  [DIAG_DOWN_LEFT_PRED ] = ff_pred4x4_down_left_mmxext;
         if (codec_id == CODEC_ID_VP8) {
             h->pred16x16[PLANE_PRED8x8] = ff_pred16x16_tm_vp8_mmxext;
             h->pred8x8  [DC_PRED8x8   ] = ff_pred8x8_dc_rv40_mmxext;